Firstly,agriculture,industry and tourism in the Yangtze River Delta,Pearl River Delta and Bohai Economic Rim were chosen to represent the primary,secondary and tertiary industries respectively,and industrial agglomeration in the three economic zones was analyzed using location quotient coefficient method.Afterwards,the critical factors influencing industrial agglomeration were discussed using gray correlation analysis.The results showed that industrial agglomeration of agriculture,industry and tourism formed gradually in the three economic zones,and the critical factors influencing industrial agglomeration were human capital,science and technology progress,and natural resources.Meanwhile,environmental pollution affected and restricted the development of industrial agglomeration.